1. Field of the Invention
The present invention relates to a control unit of a compressor compressing gas and also relates to a gas turbine power plant comprising this compressor control unit.
2. Description of Related Art
Conventionally, there is known a gas turbine fuel gas supply utility comprising a control system for adjusting a fuel gas flow rate to be supplied into a gas turbine so that a discharge pressure of a fuel gas compressor is maintained within a set range, as proposed by Patent Document 1 mentioned below, for example. This control method comprises a PI (proportional and integral) controller and two function blocks. First, the PI controller calculates a manipulation value (MV) for a by-pass valve opening. If the discharge pressure is lower than a set value, the PI controller makes the by-pass valve opening smaller. And if the discharge pressure is higher than the set value, the PI controller makes the by-pass valve opening bigger. Next, the first function block receives the manipulation value which is calculated by the gas turbine speed governing valve controller based on the gas turbine speed, and adjusts the valve opening of the governing valve located on the fuel gas piping to the gas turbine.
The first function block calculates the manipulation value such that the more the first function hock opens the governing valve, the more the fuel gas flows. The second function block receives this manipulation value as an input signal and outputs a manipulation value to make the opening of the by-pass valve smaller with the fuel gas consumption rate becoming larger, as an output signal to be added to the by-pass valve manipulation signal.(Patent Document 1) Japanese Patent No. 3137498
Nevertheless, there are actually various condition changes in the fuel gas to be supplied, such as due to the kind of fuel gas supply source (gas well or gas tank), whether there are other gas-using plants connected in parallel to the fuel gas supply source or not and a gas-using condition thereof, temperature changes according to the season, day or night, etc. In the conventional compressor control units, a gas condition of the fuel gas to be supplied into the compressor (compressor suction temperature, pressure and gas specific gravity, differential pressure between the suction side and the discharge side) is not necessarily taken into consideration so as to correspond to these changes and there is a problem that a response ability as a fuel gas supply utility is not sufficient.